1. Field of the Invention
The present invention relates to an antenna, and more particularly, to a multi-frequency antenna.
2. Description of the Related Art
With the evolution of wireless communication technology, various portable devices are exploiting wireless communication technology for data transmission, thus causing the antenna design to evolve at a rapid rate. Nowadays, these portable communication devices are becoming lighter and smaller, and the antenna must also be reduced in size in order to be installed into these electronic devices.
In terms of antenna's exterior design, the lengthy external antenna that is designed to receive and transmit radio frequency has become shorter and has been internalized, and it makes the appearance of the devices more appealing. In terms of application aspect, antenna is able to take on different shapes and sizes, thus the antennas can be designed accordingly to comply with various electronic appliance standards and to cater for different system products. Therefore, antenna manufacturing has the characteristic of high variety with low volume. However, the basic objective of designing an antenna is to improve the quality of signal transmission and reception, thus this property should not be compromised from improving its exterior appearance, size or choice of material.
Nowadays, the helical antenna and the monopole antenna are used in the circuit separately, and its pitfall is that both the helical antenna and the monopole antenna can only have a single-band frequency respectively. The applicant of the present invention has filed a TW patent application with Appl. No.: 095141199 on Dec. 7, 2006, which discloses a multi-frequency antenna combining with helix element and/or radiating element. The multi-frequency antenna comprises a helix element connecting to a feeding portion and a helix element connecting to a grounding portion. The radiating element is resonated with high frequency such as 5 GHz, and the helix element is resonated with low frequency such as 2.4 GHz. However, the multi-frequency antenna of the TW application No. 095141199 further comprises a base for fixing the radiating element and the helix element, and further for grounding and feeding.